Amphibian communities are structured by local habitat quality in garden ponds and spatial factors in urban ponds

Márton Uhrin , Barbara Barta, Beáta Szabó, Thu-Hương Huỳnh, Irene Tornero, Andrew J Hamer, Zsófia Horváth

Amphibians are among the most threatened vertebrates, and urbanisation contributes to their decline through habitat loss, fragmentation, pollution, and the spread of invasive species. At the same time, urban freshwater habitats, such as ponds, can serve as important refuges within highly modified landscapes. While the role of urban ponds in supporting freshwater biodiversity is increasingly recognised, the contribution of privately managed garden ponds remains poorly understood. Here, we compared amphibian communities in 90 ponds across Budapest, Hungary, including privately managed garden ponds and other urban ponds, to evaluate the relative importance of local environmental conditions, landscape context, and spatial connectivity. Amphibian communities differed less in taxonomic composition than in the processes structuring them. Garden pond communities were primarily shaped by local environmental filtering, whereas spatial configuration within the pond network played a stronger role in structuring communities in larger urban ponds. These results highlight contrasting mechanisms of community assembly across urban pond types. Urban amphibian conservation can therefore benefit simultaneously from local stewardship of garden ponds and strategic planning of connected urban pond networks that reduce dispersal barriers across the urban landscape.